This invention relates to medical/dental handpieces, and in particular to a disposable air-driven turbine cartridge designed for use in high-speed handpieces.
Dentists use high speed turbines in dental handpieces to rotate dental burrs at high speeds (i.e., in excess of 100,000 rpm). Surgeons use analogous handpieces when drilling or operating on bone. To enable the drill to be rotated at such high speeds, the drill bit is held by bearings and a turbine in the head of the handpiece. Air is forced into the head of the handpiece to rotate the turbine, which in turn rotates the drill bit. The air is then exhausted out the back of the handpiece. Generally the bit or bur is retained in a bur tube, and the bur tube is piloted through the turbine and the A bearings. When the bur is retained in the bur tube, the bur tube defines the axis of rotation of the turbine and the bur. For the bur to rotate about its own axis, the axis of the bur must be perfectly aligned with the axis of the bur tube. This alignment can be difficult to precisely obtain. When the axes of the bur and bur tube are not precisely aligned, the bur can wobble as it is rotated. This wobble can then make it difficult to carry out precise procedures.
When the handpiece is used, the head of the handpiece, which is inserted in the patient""s mouth, becomes contaminated. The handpiece must thus be cleaned and sterilized between uses. The most effective way to fully sterilize the hand piece is to autoclave it. However, the heat from the autoclave can, over time, damage the turbine bearings. Once the bearings have been damaged, the high speed handpiece cannot run effectively at the necessary speeds to be used as a drill. Further, grit or particulate matter can get into the handpiece. This grit can sometimes be removed by ultrasonically cleaning the handpiece. However, ultrasonic cleaning can also damage the bearings. Proper cleaning and sterilizing of the handpiece will thus effectively shorten the life of the high speed handpiece.
High speed handpieces are very expensive. To prevent the possibility of shortening the useful life of the handpiece, some dentists resort to merely wiping down the outside of the handpiece. This may clean off the contaminants on the outside of the handpiece, but it cannot not properly disinfect the exterior of the handpiece. Further, merely wiping down the outside of the handpiece does not clean or disinfect the interior of the handpiece. Grit which may accumulate in the handpiece will therefore remain in the handpiece unless the handpiece is opened and manually cleaned.
To overcome this problem, some manufacturers have introduced fully disposable high speed handpieces. One such handpiece, produced by OralSafe, of Temecula, Calif., is shown in U.S. Pat. No. 5,308,242, to McLaughlin et al. Another is shown in U.S. Pat. No. 4,842,516, to Choisser. Although fully disposable handpieces overcome the problems associated with the inability to fully clean a high speed handpiece without ruining its bearings, they are still expensive.
Currently available high speed handpieces typically include a fiber-optic cable to light the area where the doctor is working in the patient""s mouth and a water stream to cool the bit as the dentist performs a drilling operation on the patient""s teeth. Typically, the water and light outputs are located on the sleeve of the handpiece, behind the head which carries the turbine. The placement of the light and water outputs can be seen, for example, in U.S. Pat. No. 4,966,552 to Gonser. The light comes from an area behind the head of the handpiece and does not adequately light the work area in the patient""s mouth. Because the light is rather far from the drill bit, the light becomes diffused due of the longer distance traveled, and thus does a poorer job of lighting the workarea. Further, because the light comes from one direction, rather than all around the drill, it is possible that the light will be totally ineffective for use when the handpiece is used in certain angles. Similarly, with the water exiting the handpiece from the sleeve, the water is not accurately aimed at the drill bit, or may not contact the drill bit. Thus, the drill bit may not be adequately cooled during use.
High speed handpieces employ an air driven turbine to rotate the bit. Because of the high speeds at which the bit is rotated, the bit, the turbine, and the bearings in the handpiece head can become quite hot, making the handpiece uncomfortable for the dentist to hold and for the patient to have in his mouth. Although the air which drives the turbine does remove some of the heat as the air is exhausted from the unit, it would be desirable to be able to cool the head of the handpiece even further, to make the unit more comfortable for the patient to have in his mouth and for the dentist to hold.
High speed handpieces emit a high frequency sound during use of the handpiece. Studies have found that dentists who frequently use high speed handpieces show a loss of hearing at these frequencies. The sound is also typically considered to be a grating sound. It would thus be desirable to produce a handpiece which emits a sound having a lower frequency. Such a lower frequency sound would not be as bothersome to patients and dentists. Bailey, U.S. Pat. No. 5,797,743, which is incorporated herein by reference, and which is assigned to the same assignee as the current invention, discloses a disposable cartridge for use with high-speed handpieces. The cartridge disclosed in that patent works very well and solves the above noted problems. However, it does not solve the problem associated with the high frequency sound output by currently available handpieces. The medical and dental industries have long been trying to make a high-speed handpiece that will run quietly. We know of no high-speed handpiece that runs quietly or which does not produce a high pitched squeal during operation.
Briefly stated, a high-speed medical/dental handpiece removably receives a bur and is operable to drive the bur at speeds in excess of 100,000 rpm and upwards of 300,000 rpm, or faster. The handpiece includes a sleeve which carries air, water, and light to a head at an end of the sleeve. The head defines a chamber having an upper portion, a central portion, and a lower portion. The chamber lower portion has an opening therein through which the bit can pass. The chamber upper and lower portions each house a bearing and the chamber central portion houses a turbine which is positioned between, but not journaled in, the bearings. The bearings are preferably made of a low temperature plastic, such as a polycarbonate, an acetal copolymer, or an acrylate. The camber upper portion is countersunk to receive a ball bearing, against which the bit presses during operation of the handpiece. Thus, the ball bearing comprises a thrust bearing for the bit. The head includes air and water passages which direct both air and water to the turbine so that the turbine is driven by an air/water mixture.
Water is additionally passed into the upper and lower bearing chambers and is brought into intimate contact with the bit within the housing to facilitate cooling of the bit. The bearings are bobbin shaped, and, with the bearing chambers, define an upper and lower annular channels. Although the water input line could be in direct communication with both the upper and lower bearing chambers, in the disclosed embodiment, the water line is in direct communication with only the upper bearing chamber. Axial slots around the lower bearing chamber allow water to enter the lower bearing chamber from the central, or turbine, chamber. Thus, during operation of the handpiece, water is dispersed throughout the complete chamber. Preferably, the upper and lower bearings each have an axial bore which places the annular chamber in communication with the bit shaft, so that water which enters the annular channels will flow through the bearing passages to contact the bit. Additionally, water is drawn into the interface between the bearings and the turbine. The chamber is provided with a plurality of exhaust ports on a lower surface of the chamber through which the air/water mixture in the head is exhausted. Thus, a separate exhaust line which extends through the handpiece is not required. The size and number of exhaust ports reduces the velocity of the exhausted air/water mixture.
The handpiece head is preferably a disposable cartridge which is received on an autoclavable sleeve. The cartridge includes a body removably mountable to the sleeve and a cap mounted to the body. The body and cap cooperate to define the chamber. The cartridge body includes a hollow sleeve portion and a head portion. The cartridge body sleeve portion is slidably mounted over an end of the handpiece sleeve. The cartridge body sleeve includes a snap arm having an inwardly directed finger at a free end thereof which engages the handpiece sleeve to hold the cartridge on the sleeve. The cartridge sleeve also includes a release arm operatively connected to the snap arm by a fulcrum; whereby, the snap arm finger is brought out of engagement with the handle by pressing down on the release arm.
The cap includes a heel (or back portion) which, when the cartridge is placed on a handle or sleeve, abuts a light tube. The cap includes a lens beneath the heel which directs light from the light tube toward the bit. At least the cap heel and lens are translucent or transparent to allow light to pass into the cap and through the lens. The cap also includes a reflective surface in the heel which directs light from the light tube into the lens.